Field of the Invention
Embodiments of the present disclosure relate generally to power line communication (PLC) and, in particular, to PLC via three phase power lines.
Description of the Related Art
Power Line Communications (PLC) is a technology for utilizing power lines, such as the existing commercial AC power grid infrastructure, to communicate data between devices coupled to the power lines. For PLC transmission, a transmitter is generally coupled to the power line through an isolation transformer and injects a modulated carrier signal as a voltage stimulus on the power line (i.e., a voltage-based signal). A receiver coupled to the power line receives the modulated carrier signal and decodes the signal to recover the originally transmitted data.
For PLC over three-phase power lines, the communication signal may be injected onto all three phases of the power lines; alternatively, all three power lines may be coupled to one another with sufficiently large capacitors and the communication signal may be injected onto one of the phases of the power lines. Such configurations present several disadvantages. For example, a neutral line, or in some cases ground line, is required for a return line. When utilizing the power line ground as the return line, large capacitors rated for very high surge voltages must be used to couple between line to ground, increasing the cost of the overall communication system. Further, since some industrial applications don't require a neutral line, one must be run for such installations if the neutral line is to be used for the return path, greatly increasing the wiring cost for the system. Additionally, such PLC configurations suffer from imbalance as a result of the signal being carried on all three phases of the power line on one side but only on a neutral line on the return, resulting in radiated emissions as well as sensitivity to external noise.
Therefore, there is a need in the art for a method and apparatus for efficient three-phase power line communication.